Method and means for striking and sustaining alpha low-voltage arc



Sept. 29, 1925.- 1,555,547

' J. BETHENOD METHOD AND- MBANS FOR STRIKING AND SUSTAINING A LOW VOLTAGEARC Filed Nov. 2'7. 1923 erators of a special type'delivering Patented Sept. 29, 1925.

.rosarn nnrnnnon, or rams, rnancn METHOD .ALID MEANS FOR STBIKIING AND SUSTAINING A LOW-VOLTAGE ARC.

Application filed November 2?, 1928. Serial No. 677,824.

To all whom it may concern.

Be it known that I, Josnrn BETHENOD, citizen of the Republic of France, residing at 15 Rue Michel-Ange, Paris, XVI", in the Republic of France, have invented certain new and useful Methods and Means for Striking and Sustaining a Low-Voltage Arc, of which the following'is a specification.

It is already well known in electric welding and like work (arc metal cutting etc.) to use a low tension electric are fed by means of either a direct current or alternating current source. In order to obtain satisfactory results, it is necessary that such are lights up easily and, once lighted, keeps burning on, even if its length isappreciably varied as much as is needed owing to the work tobe done. With direct current there are commonly used, as well known, gena relatively high no-load voltage, but the short circuit current of which cannot however much exceed the normal current; such gencraters are costly and bulky.

When alternating current is used the problem is yet lhuch more difiicult to solve, "on account of the fact that a low tension arc between metal electrodes is diificult to keep burning. In order to obtain a sufficientnoload voltage, without the short circuit current rising to an excessive value, a suitable impedance is generally connected in between the arc and the mains. This, however implies important supplementary losses or 'ves rise to a very small power factor. In i'ief the working is never quite good, and, in most cases, the use of direct current is preferred, by generating it locally,'if needed,

y means of a motor-generator unit.

The object of my present invention is a method and means, by which alternating 'current may be used at a very low tension (40 volts, for instance) for electric arc weldmg or similar applications.- It is to be noted, however, well be applied direct current, and gives then, as one of its advantages, the possibility of using, as a current source,small storage batteries, such as are commonl used on motor-cars for various duties (h hting, ignition, starting). The setting up 0 portative welding out ts is then, owlng to my-invention, quite simple and the fact that such outfits may be used anywhere (for instance for immediate rethat my method may equally in the case use is made of a' terminals 3 and moreover the sparks maintain a sufficient ionization between the said electrodes to easily keep the are burning even if the feeding source is an alternating current one. It has already been proposed to produce such a voltaic are between electrodes not in contact, but the methods which were used do not seem to have given till now any satisfactory results, principally as regards the application to which my invention is directed. The method which is the object of my present invention. gives, on the contrary, excellent results, as has been shown by experience. This method consists, in its principle, in connecting across the arc terminals a condenser Which is included in an oscillating circuit fed by means of a high frequency current source of any .typc. Between the electrodes is thus produced a high tension which givesrise to the spark used to start and maintain the are. As this condenser has a relatively very small capacity it does not take any noticeable supplementary output current from the are feeding source, which last is protected from the high frequency current by the ordinary means of choking coils. Moreover, it is to be noted that the power dissipated inthe whole of the high frequency circuits is relatively quite small in comparison with the power delivered to the arc.

Figure 1 shows a preferred form of my invention as applied to the feeding of an are, between electrodes land 2, bymeans of alow tension current source not shown, the output circuit of which should be connected across 4. According to a known disposition a self inductance choking coil 5 is inserted, into the circuit. According to my invention, I apply across the arc terminals a high frequency elect'romotive force, which in the example shown, is supplied by means of an oscillatory circuit comprisly easier numg a condenser 6 across the arc terminals,

a self-induction coil 7 andanother condenser 8. This circuit is excited by means of a highv frequency generator 18, the output terminals of which are diagrammatically shown at 16,

17 and the in ut terminals of which are diagrammatica 1y shown at 14 and 15, as

connected through some regulating means 12 (variable resistanceor impedance) with the low voltage mains 34. By tuning circuit 6, 7, 8, on the, frequency of generator 18, one may obtain, as is well known a tension as high as is wanted, across he ter-.

minals of condenser 6, that is to say across the arc, WlllCll can thus, in any case,

be ignited and kept burning. It must be understood that, in such tuning, the capacity of electrodes 1 and 2 to each other must be taken into account.

Another object of condensers 6 and 8 is to avoid short circuiting the low frequency mains, self induction coil 5 avoiding any high frequency current from passing into the said mains.

A second form of my invention is shown on Figure 2 in which thev same letters are employed to designate the same parts asin Figure 1 and in which the high frequency generator shown at 18 on Figure 1 is represented in the known form of an oscillatory} circuit with spark gap 13, capacity 10 and self-induction 9, inductively coupled to. selfinduction 7 of the above described oscillatory circuit 6, 7, 8. Condenser 10- is charged by means of a transformer 11, the primary r winding of which is fed by means of a across terminals 3.4. a I

In the case where direct current means are used oscillating circuit 6, 7, 8, may be excited by means of an induction coil with vibrator, fed, for instance, from the said direct current mains.

In any case, the high frequency current source could be in the form of a highfrequency alternator, a vacuum tube, an arc of the Poulsen type, etc. or of any other source generall known for high frequency,

currents, the said source replacing parts 9,

10, 11, 12, 13, ofthe Figure 1. These parts falling off, the high frequency source may be introduced into circuit 6, 7, 8, with or without the use of a transformer. However, in each of the above described dispositions, the use of condenser 6 remains essential.

It is to be noted, at last, that the-high frequency current is, as well known, without any physiological efi'ect [on the operator,

although a high tension will be produced-on the charging of condenser 6 .by' such current.

Having thus described my invention, what I claim 'as new and desire'to. secure by Letters-Patent is:

l. The method of striking and in char ing perio ically said'condenser by means 0 an auxiliary source.

a 2. Electric arc apparatus comprising in combination a low tension current source, two electrodes connected thereto, a condenser directly connected across the said electrodes and an auxiliary source adapted to charge periodically said condenser.

j 0 v '3. Electric apparatus comprising in combinatlon, a low tension current source, two

electrodes connected thereto, a condenser di- I and sustaining a low voltage arc, WlllCh consists in connectmg a condenser dlrectl across the arc point,

rectly connected across the said electrodes,

said condenser being part of a closed oscillatory circuit, and a relatively high frequency current source adapted to feed said closed oscillatory circuit.

4. Electric arc apparatus comprising in" combination a low tension current source,

two electrodes connected thereto, a condenser directly connected across said electrodes, said condenser being part of a closed oscillatory circuit comprising also an inductance and another condenser and a relatively high frequency current source adapted to energize said closed oscillatory circuit.

- 5. Electric arc apparatus comprising in combination a low tension current source, two electrodes connected thereto, a condenser directly connected across said electrodes, said condenser being part of a closed oscillatory circuit comprising also an inductance and another condenser and a relatively high frequency current source adapted to energize said closed oscillatory c1rcuit, said closed oscillatory circuit being tuned to the frequency of said relatively high frequency current source.

In testimony whereof I affix my signature.

JOSEPH. BE' IHENOD. 

